Continuous measurement of coronary artery diameter in situ

The diameter of the coronary artery was measured in dogs in situ by an ultrasonic dimension gauge using 10-MHz piezoelectric crystals. Underestimation in measurements due to crystal rotation was limited to < 1% by adding a convex lens to the crystal. A pair of small 10- and 5-MHz crystals were sutured to the adventitia of the left circumflex coronary artery (LCX) and the descending aorta (Ao), respectively. Using cuff occluders for vessel constriction of the inferior vena cava (IVC) or the Ao, curvilinear relationships between pressure and diameters were obtained. Phasic changes of the aortic as well as coronary diameter were grossly similar to changes in the pressure wave. After intravenous administration of dipyridamole, aortic pressure (AP) decreased by 17% along with 3% decline of the Ao and LCX diameter, however, after nitroglycerin given by the same route, LCX diameter increased by 5% (P < 0.05) despite 16% and 2.3% reductions in AP and Ao diameter, respectively. This ultrasonic technique, which allows continuous measurement of the diameter of small vessels, should provide a new tool for the study of coronary circulation.